CS363

1. Week 10 - Wednesday CS363

2. Last time • What did we talk about last time? • Network basics

3. Questions?

4. Project 3

5. Assignment 4

6. Security Presentation Cody Kump

7. Eavesdropping

8. Eavesdropping and wiretapping • Eavesdropping means overhearing private information without much effort • Administrators need to periodically monitor network traffic • Wiretapping implies that more effort is being used to overhear information • Passive wiretapping is only listening to information • Active wiretapping means that you may adding or changing information in the stream

9. Cable wiretapping • If you are on the same LAN, you can use a packet sniffer to analyze packets • Packets are constantly streaming by, and your computer usually only picks up those destined for it • Passwords are often sent in the clear • Wireshark is a free, popular packet sniffer • Cable modems are filters that give you only the data you need • Sophisticated attackers can tap into a cable network • Data is supposed to be encrypted, but many networks don’t turn encryption on • Inductance is a property that can allow you to measure the signals inside of a wire without a direct physical connection • Using inductance or physically connecting to a wire changes its impedance, which can (but usually is not) measured • Signals are often multiplexed, sharing media with other signals, which can increase the sophistication needed to wiretap

10. Wireless eavesdropping • Wireless networks are easy to disrupt, but attackers usually have little to gain by this • Since they are broadcast, it is not difficult to intercept the signal • Special antennas can receive the signal from a longer distance than usual • Some networks are entirely unencrypted • WEP is almost completely broken • WPA and WPA2 have vulnerabilities that can be exploited in some cases

11. Other media • Microwave is easy to intercept • Long distance phone can use microwaves • Cell phones can use microwaves • One difficulty with making use of the intercepted signal is that microwave signals are heavily multiplexed, making it hard to untangle individual signals • Satellites are similar (unsecure but heavily multiplexed) • Optical fiber is very difficult to tap • Cutting a single fiber means recalibrating the network • Repeaters and taps that connect the fiber are the best places to attack

12. Impersonation • Rather than wiretapping, attackers will more often try to impersonate a legitimate user • Different approaches: • Guess the identity and authentication information • Use other communications or wiretapping to gain such information • Circumvent the authentication mechanism • Use a target that will not be authenticated • Use a target with known authentication data

13. Authentication issues • Passwords are often easy to guess • Because we’re bad at picking passwords • Because the user may not have realized that the machine would be exposed to network attacks • Passwords are sent in the clear • Bad hashes can give information about the password • Sometimes buffer overflows can crash the authentication system • Sometimes authentication is not needed • .rhosts and .rlogin files in Unix • Guest accounts • Default passwords on routers and other devices that never get changed

14. Authentication attacks • Spoofing is when an attacker carries out one end of a networked exchange • A masquerade is spoofing where a host pretends to be another host • URL confusion: someone types hotmale.com (don’t go there!) or gogle.com • Phishing is a form of masquerading • Session hijacking (or sidejacking) is carrying on a session started by someone else • Login is encrypted, the rest of the data often isn’t • Firesheep allows you to log on to other people’s Facebook and Twitter accounts in, say, the same coffeeshop • Man-in-the-middle attacks

15. Confidentiality threats • Misdelivery • Data can have bad addresses, occasionally because of computer error • Human error (e.g. James Hughes (student) instead of James Hughes (professor)) is more common) • Exposure of data can happen because of wiretapping or unsecure systems anywhere along the network • Traffic flow analysis • Data might be encrypted • Even so, it is very hard to hide where the data is going to and where it is coming from • Tor and other anonymization networks try to fix this

16. Integrity threats • Attackers can falsify some or all of a message, using attacks we’ve talked about • Parts of messages can be combined • Messages can be redirected or deleted • Old messages can also be replayed • Noise can degrade the signals • All modern network protocols have error correction built in • Malformed packets can crash systems • Protocols often have vulnerabilities

17. Web site vulnerabilities • Web sites are supposed to be up all the time • They can be studied and attacked over a long period of time • Known vulnerabilities in web servers allow hackers (even unsophisticated ones) to gain control of web sites and deface them • Buffer overflows can crash web applications • URL and SQL injection attacks • If web applications are poorly written, they may blindly execute whatever is passed into the URL • Could point to ../../../sensitive.dat, gaining access to files in other directories • Could give SQL to destroy or publicize the contents of the database • Server-side includes can tell the server to do specific things, but they can be manipulated by attackers who cleverly edit the HTTP requests

18. Denial of service • Networks are one of the best places to launch an attack on availability • In this setting, these are usually called denial of service (DoS) attacks • Transmission failure can happen because a line is cut or because there is too much noise • Flooding is a common technique • Ask for too many connections • Request too many of some other service

19. Three way handshake • TCP is built on a three-way handshake • Client requests a connection by sending a SYN packet • The server acknowledges the request by sending a SYN-ACK packet back • The client responds with an ACK, establishing the connection • An attacker can just keep sending SYN packets • The server will allocate some resources, wait for the ACK, and never get it • A clever attacker will spoof at least his own IP so that the SYN-ACK is sent elsewhere • A more sophisticated attacker will spoof many different IP addresses (or have many bots in a botnet) sending all these SYN's

20. Denial of service attacks • Echo-chargen • Chargen sets up a stream of packets for testing • Echo packets are supposed to be sent back to the sender • If you can trick a server into sending echo packets to itself, it will respond to its own packets forever • Ping of death • A ping packet requests a reply • If you can send more pings than a server can handle, it goes down • Only works if the attacker has more bandwidth than the victim (DDoS helps) • Smurf • A ping packet is broadcast to everyone, with the victim spoofed as the originator • All the hosts try to ping the victim • The real attacker is hidden • Teardrop • A teardrop attack uses badly formed IP datagrams • They claim to correspond to overlapping sequences of bytes in a packet • There’s no way to put them back together and the system can crash

21. Distributed denial of service • Distributed denial of service (DDoS) attacks use many machines to perform a DoS attack • Usually, many targets have been compromised with a Trojan horse making them zombies • These zombie machines are controlled by the attacker, performing flooding or other attacks on a victim • The attacker is hard to trace

22. DNS attacks • The Domain Name System (DNS) uses Domain Name Servers (also DNS) to convert user readable URLs like google.com to IP addresses • Taking control of a server means that you get to say where google.com is • For efficiency, servers cache results from other servers if they didn’t know the IP • DNS cache poisoning is when an attacker gives a good server a bad IP address

23. Active and mobile code threats • Cookies • Small files saved by your browser on your disk • Can be per-session or persistent • Intercepted cookies can allow impersonation • Server side scripting • Includes ASP, JSP, and PHP • Again, poorly sanitized inputs can cause arbitrary code to be executed on the server • Active code • Java applets are run in a sandbox, preventing them from accessing most of your system • Some JVM implementations had weaknesses allowing them out • ActiveX is Microsoft’s system for running code in a browser • It has far too much power and can do anything to your system • Usually, you have to click a button to allow the ActiveX control to run

24. Summary of vulnerabilities

25. Network Security Controls

26. Architecture • Good network architecture can make security better • Segmentation means separating the network into different parts • Web server • Database server • Application servers • Redundancy is important • Multiple servers that check if each other have gone down • Avoid single points of failure

27. Encryption • Encryption is important for network security • Link encryption encrypts data just before going through the physical communication layer • Each link between two hosts could have different encryption • Message are in plaintext within each host • Link encryption is fast and transparent • End-to-end encryption provides security from one end of the transmission to the other • Slower • Responsibility of the user • Better security for the message in transit

28. Virtual private networks • Encryption that allows people in a public network to communicate securely with a private network creates a virtual private network (VPN) • A user’s system negotiates a key with a firewall that guards a private network • Communication takes place in a tunnel

29. Public key infrastructure • As we discussed before, the big problem with public keys is making sure you get the right one • Public key infrastructure (PKI) is the solution to this problem • A PKI sets up certificate authorities who certify that keys belong to who they’re supposed to • Their jobs include: • Managing public key certificates • Issuing certificates that connect a user to a key • Scheduling certificate expiration • Publishing certificate revocation lists

30. Secure protocols • SSH (secure shell) is a protocol for encrypted communication between computers • Designed for Unix/Linux, but available on Windows • Telnet, rlogin, and rsh should be replaced by SSH • Negotiates symmetric key encryption usually using public key encryption, similar to Project 2 • SSL (secure sockets layer) or TLS (transport layer security) creates a secure session (golden lock) between a web browser and a web server

31. IPSec • IPSec (IP Security Protocol Suite) is a group of protocols designed to provide security for general IP communication • There is an Authentication Header (AH) mode that provides authentication and integrity by supplying a cryptographic hash of the message and its addresses • There is an Encapsulated Security Payload (ESP) mode that can provide encryption, authentication, or both • In transport mode, IPSec encrypts only the payload of the packet • In tunnel mode, IPSec encrypts the entire packet and puts it inside of another packet, hiding its final destination inside of a private network

32. Content integrity • Encryption helps protect integrity from malicious attackers • Error correcting codes (like parity checks) can help prevent non-malicious problems with integrity • Cryptographic checksums (AKA cryptographic hash digests) protect from both malicious and non-malicious threats to integrity

33. Strong authentication • Who are you talking to? Passwords can be stolen • One-time passwords prevent the problem of stolen passwords • RSA SecurIDs and other password tokens generate one-time passwords • Challenge-response systems serve a similar role • Kerberos is a system designed at MIT • Users interact with an authentication server who authenticates them • They get a ticket to access a file from a ticket granting server • The ticket lets you use a file • Everything is time-stamped

34. Access controls on routers • Routers want to block packet floods from affecting the servers behind the router • We can have ACLs that list all the legal (or all the illegal) hosts that can send (or are not allowed to send) packets into the network • But, checking packets against ACLs slows down the system, making the router easier to flood • Since it is possible to forge source addresses, the ACLs might not correctly block the packets

35. Wireless security • A wireless access point has a Service Set Identifier (SSID) • SSIDs are usually broadcast, weakening security • Even non-broadcast SSIDs can be discovered whenever someone connects to them • Wired Equivalent Privacy (WEP) was the old standard for encryption • Tools like WEPCrack and AirSnort can break WEP in minutes because of flaws in the RC4 encryption algorithm • WiFi Protected Access (WPA) and later WPA2 have better security • Encryption keys change for each packet • Several authentication mechanisms are allowed • WPA2 can use AES • There are still flaws in some implementations, as discussed by Mark Yorgey

36. Firewalls

37. Firewalls • A firewall filters traffic between an inside network and an outside network • The inside is more trusted and needs to be protected from the outside • Kinds of firewalls: • Packet filtering gateway or screening routers • Stateful inspection firewalls • Application proxies • Guards • Personal firewalls

38. Packet filtering gateway • Packet filtering gateways are simple • They only allow certain packets to get by • Based on source or destination address • Based on protocol (HTTP on port 80, for example) • A packet filter can be used in combination with other firewalls • The packet filter can remove a lot of traffic so that a more complex firewall has to worry about checking fewer packets • Packet filters ignore the data inside the packets • They only use the addresses and port numbers

39. Stateful inspection firewall • A stateful inspection firewall keeps track of data inside of packets • For example, if a host inside the firewall initiates a TCP connection with a host outside, a stateful inspection firewall can remember this and let only that particular outside host’s packets in

40. Application proxies and guards • An application proxy gateway (or bastion host) appears to function like a host running a particular application • The outside world sends date to the application proxy’s IP address • The application proxy changes the addresses and forwards the data on to the real server • Only appropriate requests and responses are allowed through • All accesses can also be logged • A guard is really the same thing, just with more functionality • For example, a guard might reassemble a file and run it trhough a virus scanner

41. Personal firewalls • A personal firewall is software that runs on a workstation • These firewalls can give additional protection • The user and OS can have very fine grained control over what kind of connections can be made and what kind of applications can send and receive data

42. Upcoming

43. Next time… • Finish firewalls • Intrusion detection • Secure e-mail • Review for Exam 2 • Andrew Sandridge presents

44. Reminders • Read Sections 7.3 through 7.6 • Finish Assignment 4 • Due on Friday • Study for Exam 2 • Next Monday